Notes swap mémoire

Voir :

https://chrisdown.name/2018/01/02/in-defence-of-swap.html

https://kubernetes.io/blog/2025/03/25/swap-linux-improvements/

Voir aussi :

Swap sur ramdisk

systemctl --type swap cat /proc/swaps cat /proc/vmstat
echo 0 > /proc/sys/vm/swappiness # cat /proc/sys/vm/vfs_cache_pressure # sysctl -w vm.vfs_cache_pressure=50
# Allocate storage and restrict access fallocate --length 4GiB /swapfile chmod 600 /swapfile # Format the swap space mkswap /swapfile # Activate the swap space for paging swapon /swapfile

Analyse consommation

Consommation de la SWAP par utilisateur

smem -u -s swap

Consommation de la SWAP par process

smem -s swap

ou

echo -e "SWAP_KB\tPPID\tPID\tEXE" for S_FILE in /proc/[0-9]*/ ; do S_PPID="$(awk '/^PPid:/ { print $2}' ${S_FILE}/status)" ; S_PID="$(echo ${S_FILE}/status | cut -d'/' -f3)" ; S_EXE="$(readlink $S_FILE/exe)" ; S_SWAPKB="$(awk '/VmSwap/ { print $2}' ${S_FILE}/status)" ; [ ! -z $S_SWAPKB ] && echo -e "$S_SWAPKB\t${S_PPID}\t${S_PID}\t${S_EXE}" ; done | sort -n

dphys-swapfile

dphys-swapfile swapoff

Recommandations SWAP

Prereq Oracle

RAM	Swap Space
Between 1 GB and 2 GB	1.5 times the size of the RAM
Between 2 GB and 16 GB	Equal to the size of the RAM
More than 16 GB	16GB
RAM	Swap Space
Between 8 GB and 16 GB	Equal to the size of the RAM
More than 16 GB	16GB

Recommandations RedHat

Source : https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/managing_storage_devices/getting-started-with-swap_managing-storage-devices

Amount of RAM in the system	Recommended swap space	Recommended swap space if allowing for hibernation
⩽ 2 GB	2 times the amount of RAM	3 times the amount of RAM
> 2 GB – 8 GB	Equal to the amount of RAM	2 times the amount of RAM
> 8 GB – 64 GB	At least 4 GB	1.5 times the amount of RAM
> 64 GB	At least 4 GB	Hibernation not recommended